A test handler is an apparatus for testing semiconductor devices in a certain test environment to inspect the qualities of the semiconductor devices after they are fabricated. Techniques related to the test handler are disclosed in many published documents including Korean Patent Publication No. 2003-0029266 (entitled “Test Handler”).
To conduct a test by using the test handler, it is required to transfer semiconductor devices from a customer tray, which is used to accommodate the semiconductor devices after their fabrication, into a test tray, which is used to accommodate the semiconductor devices during the test. After the completion of the test, the semiconductor devices should be transferred back into the customer tray. The present invention pertains to a pick and place apparatus for transferring the semiconductor devices between the customer tray and the test tray. For the purpose, the pick and place apparatus includes a plurality of device holding elements operated to grasp or quit the grasp of the semiconductor devices.
As for the customer tray, since the customer tray is used to load or store the semiconductor devices therein, the customer tray is designed to provide a small interval between the semiconductor devices loaded therein to accommodate as many semiconductor devices as possible on the same area. Meanwhile, since a certain amount of interval needs to be maintained between the semiconductor devices for the test of the semiconductor devices, the test tray is designed to provide a relatively larger interval between the semiconductor devices loaded therein, in comparison with the customer tray.
Accordingly, the pitch between the device holding elements of the pick and place apparatus should be at a minimum level when they pick and grasp the semiconductor devices from the customer tray or quit the grasp of the devices, while the pitch should be at a maximum level when the device holding elements pick and grasp the semiconductor devices from the test tray or quit the grasp of them. For the purpose, the pick and place apparatus needs to have a means for controlling the intervals between the plurality of device holding elements in a preset arrangement. Techniques related thereto are disclosed in Korean Patent Publication No. 10-1998-033607 (entitled “Pick and Place of Semiconductor Device Test Equipment”: Reference 1), Korean Patent Publication No. 10-2002-0061194 (entitled “Pick and Place of Semiconductor Device Test Equipment”: Reference 2), and so forth.
Reference 1 describes a technique for controlling horizontal pitches between device holding elements by connecting them with a link and supplying power to device holding elements at both ends of the array as translational forces for moving them horizontally in opposite directions. Reference 2 discloses a technique for controlling horizontal pitches between device holding elements by way of supplying a translational force in horizontal direction to all of the device holding elements by using a cam plate, and it also proposes a technique for controlling the pitches by using a cam shaft.
In accordance with Reference 1 or Reference 2, there should be prepared a linear motion guide mechanism for guiding horizontal movements of the device holding elements, as exemplified in Reference 2 (slide members assigned as reference numerals 35 and 36 in Reference 2).
Among various linear motion guide mechanisms, a LM guide, a ball spline, or the like are used for the pick and place apparatus. The LM guide or the ball spline has a guide rail and coupling blocks configured to be slid along the guide rail, wherein the device holding elements are fixed at the coupling blocks via, e.g., bolts or the like. If the sizes of the guide rail and the coupling blocks are set to be large, the device holding elements can be more firmly coupled to the coupling blocks and the stability of the horizontal movements of the device holding elements can be improved, resulting in enhancement of endurance and reliability of the entire pick and place apparatus. However, the size increase of the guide rail and the coupling blocks would also result in the problem of weight increase of the apparatus. If the sizes of the guide rail and the coupling blocks are reduced, on the other hand, the endurance and reliability of the pick and place apparatus would be reduced, though the apparatus can be made lighter.
Meanwhile, in the conventional pick and place apparatus, a first and a second linear motion guide mechanism are vertically arranged in parallel to each other while maintaining a predetermined interval therebetween, and each of the device holding elements is engaged with both of the first and the second linear motion guide mechanism to be guided by them horizontally.
However, the conventional pick and place apparatus, which has the configuration where each of the device holding elements is engaged with both of the linear motion guide mechanisms, has structural limits in its size, operational characteristics and production efficiency. Those limitations will be described hereinafter with reference to FIG. 1 showing an example using LM guides as the linear motion guide mechanisms.
First, in case of fixing a device holding element 11 at an LM block (coupling block) 13a of a LM guide 13 by using bolts 12, the bolts 12 need to be fastened with a great torque to increase the endurance of the pick and place apparatus. However, since the tightening torque for the bolts 12 should be set in proportion of the size of the LM block 13a, there is a limit in increasing the tightening torque of the bolts 12. Specifically, if the LM block 13a has a relative large size, the LM block 13a would not be deformed by a bolt tightening torque even though the bolt tightening force is set to be great, whereas if the size of the LM block 13a is small, the LM block 13a would be readily deformed by the bolt tightening torque, thus being brought into excessively close contact with the LM rail 13b. For the reason, the tightening force for the bolts 12 should be set in proportion to the size of the LM block 13a. Accordingly, to increase the endurance of the pick and place apparatus, it is preferable to use a LM guide 13 of a large size having a large LM block 13a. Further, since the sizes of the LM block 13a and the LM rail 13b are in proportion to the stability of linear movements of the device holding element 11, the LM block 13a and the LM rail 13b are required to have large sizes in the aspect of improving the reliability of the pick and place apparatus as well. That is, if the LM block 13a has a relatively small size or the LM rail 13b has an excessively small vertical width, the linear motion characteristic of the LM guide 13 would be degraded by a moment or a weight applied to the LM block 13a. Therefore, a LM guide 13 of a large size is preferred.
In contrast, to reduce the size of the pick and place apparatus, the LM block 13a is required to be as small as possible. Though the size (especially, the width) of the LM block 13a may not have a great influence on the entire size of the apparatus if only one LM block 13a is used for the LM rail 13b, the width of the LM block 13a would be an important factor for determining the entire size of the pick and place apparatus given that the apparatus has a configuration in which a plurality of device holding elements 11 are horizontally arranged (in general, eight device holding elements are arranged in a row). Therefore, a LM guide 13 of a small size is preferred.
Among the characteristics of the pick and place apparatus as described above, the size and the weight of the apparatus would have a greater impact on the entire performance (reaction time, operational accuracy, etc.) of the test handler than the endurance and the reliability of the apparatus. Thus, a small-size LM guide with a LM block of a small width is usually employed in the field, bearing the low endurance and reliability of the apparatus. Thus, the cycle of maintenance of the pick and place apparatus is very short. Specifically, when using a small-size LM guide with a LM block of a small width, though it is intended to complement the bolt coupling force between the device holding element and the LM block is intended, such a coupling method is incomplete in view of the characteristic of the pick and place apparatus that its operation is repeated for a long period of time. Thus, frequent maintenance works are needed.
Further, if the LM guide 13 is designed to have a size smaller than the required size to reduce the size of the pick and place apparatus, the bolt tightening torque having a direct influence on the operational characteristic of the LM guide 13 should be controlled very precisely in the manufacturing process of the pick and place apparatus, which is very troublesome. If the bolt tightening torque is greater than a tolerance of the LM block 13a, the LM block 13a would suffer deformation and would be brought into excessively close contact with the LM rail 13b, thus hampering the horizontal movements of the device holding elements 11. Thus, when using the LM guide 13 whose size is smaller than the required size, a precise control of the bolt tightening torque is needed, which would result in deterioration in production efficiency and increase of production of inferior goods.
Moreover, in the configuration where each device holding element 13 is engaged with both of the LM guides 13 and 14, the LM guides 13 and 14 should be fabricated in a pair for the reason of existence of mutual limitations between the pair of LM guides 13 and 14. Accordingly, the unit cost of the LM guides 13 and 14 increases, resulting in increase of manufacturing costs of the pick and place apparatus.
In addition, as disclosed in Korean Patent Application No. 2005-17464 that was commonly assigned to the applicant of the present invention prior to the filing date of the present application, in a configuration where each device holding element 11 is engaged with both of the two LM guides 13 and 14 and a power supply mechanism having a power transmission shaft such as a screw guide shaft for guiding the movements of the device holding element 11 while transmitting a moving force thereto, a vertical (Z-axial) tolerance and a parallelism between the upper LM guide 13 and the lower LM guide 14 should be controlled as well as a vertical (Z-axial) tolerance and a parallelism between the upper LM guide 13 and the screw guide shift and a vertical (Z-axial) tolerance and a parallelism between the lower LM guide 14 and the screw guide shift. Actually, however, it is impossible to set the Z-axial tolerances and parallelisms of three different related parts in a general manufacture or assembly technique. Thus, the unit cost of a frame of the pick and place apparatus having the LM guides 13, 14 and the screw guide shaft fixed thereat would be increased, which would result in a great increase of manufacturing costs of the pick and place apparatus.